If you're looking for manga similar to Dansui!, you might like these titles.
Third-year high school student Aya, who's secretly afraid of water, manages her high school's swim club. It's her last summer as manager and her final time managing the swim club for the Inter High Meet, but perceptive Takeru figures out her secret.
Nanase Haruka is a sixth-grade elementary school student who loves connecting with the water and feeling the water as he swims, and he attends a local swim club together with his childhood best friend Tachibana Makoto and Hazuki Nagisa, one year younger than the both of them. Then, one winter’s day as graduation draws near, Matsuoka Rin transfers into Haruka and the others’ school from another swim club. Through swimming, Haruka strengthens his bonds with Makoto and Nagisa, as well as with Rin–at which point Rin, with his passion for the medley relay, suggests they form a team together and enter a tournament.
In search of her mother, Nagi, a girl from a desolate country village, comes to a big city and enters Swimming Suieikyou High School. Shortly after joining the swimming club, Nagi finds out that the pool is actually completely dominated by boys! But in this never-practicing so-called swimming club Nagi finds something...
The story is a prequel of the anime Free! and happens during the elementary school time of the boys Haruka, Rin, Makoto and Nagisa.
Konashi is a hard-working swimming buff who's focused on becoming good enough to land himself a spot in the upcoming summer swim competition. One day while heading to the pool to swim as always, he spots a guy he's never seen before standing on the jumping board with his clothes and shoes still on. As it turns out he's Eguchi, the resident class "mystery" who's only ever attended one of his classes. As they get talking, Konashi realizes he's nothing like the rumours made him out to be and so began a quirky brief friendship that leaves a strong impression on him even years later.
Hisui used to live on Kohaku Island, where she lived by the ocean and loved life. However, she’s changing schools and thus has to leave her best friend, Kairi the dolphin, behind… It’s at that time, Hisui meets the swim team’s hot Minato by chance…! Could this be a blooming love for the attractive boy, or a replacement for her dolphin Kairi?
Umi has just transferred schools, and she's all set with a dream of putting together a team of ultimate swimmers, called the Splash Five! While recruiting talented boys to wear speedos, will she end up falling in love...?